In the human body, oxygen is absrobed by the lungs and nutrients are absorbed by the small intestine. in a single-celled organism, what this absorption directly involves

cell membrane

Explanation:

Single cell organisms like the bacteria depend mostly on diffusion for gaseous exchange. They take in food that does not require complex digestion processes. The cell membrane is selectively permeable and allows absorption of nutrients like glucose that have molecules of small size.

c.) polymerase chain reaction

- "unlike the original dna fingerprinting method, dna profiling does not use restriction enzymes to cut the dna. instead it uses the polymerase chain reaction (pcr)? to produce many copies of specific str sequences. pcr is an automated procedure that generates lots of copies of a specific sequence of dna."

c. establishing proper sleep hygiene